[Ace] Barry Leiba's No Objection on draft-ietf-ace-coap-est-17: (with COMMENT)

[Barry Leiba via Datatracker <[e-mail]>]

Barry Leiba has entered the following ballot position for
draft-ietf-ace-coap-est-17: No Objection

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COMMENT:
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Thanks for this — a useful document.  I have a bunch of comments, but they’re
all editorial.  Please consider them, but there’s not a need to give a detailed
reply.

-- Section 4 --

      In that case, the
      server MAY want to authenticate a client certificate against its
      trust store although the certificate is expired (Section 10).

Total nit: Why "want to"?  Why not "server MAY authenticate"?

   As described in Section 2.1 of [RFC5272] proof-of-identity refers to
   a value that can be used to prove that the private key corresponding
   to the certified public key is in the possession of and can be used
   by an end-entity or client.

I find the passive voice to be quite awkward here, and suggest making it active:

NEW
   As described in Section 2.1 of [RFC5272], proof-of-identity refers
   to a value that can be used to prove that an end-entity or client is
   in possession of and can use the private key corresponding to the
   certified public key.
END

   the event of handshake message fragmentation, the Hash of the
   handshake messages used in the MAC calculation of the Finished
   message must be computed as if each handshake message had been sent
   as a single fragment (Section 4.2.6 of [RFC6347]).

I know this wording is directly from 6347, but I think it's unclear and would
like to suggest an alternative.  The "as a single fragment" part is odd,
because I think what it's really saying is that it's computed as if it had not
been fragmented.  My suggestion is to change it thus (and similarly for the
next paragraph after):

NEW
   the event of handshake message fragmentation, the Hash of the
   handshake messages used in the MAC calculation of the Finished
   message must be computed on each reassembled message, as if
   each handshake message had not been fragmented (Section 4.2.6
   of [RFC6347]).
END

If that's not correct, please take that as further evidence that it's unclear,
and adjust accordingly.

   To alleviate this
   situation, an EST-coaps DTLS connection MAY remain open for
   sequential EST transactions which was not the case with [RFC7030].
   For example, an EST csrattrs request that is followed by a
   simpleenroll request can use the same authenticated DTLS connection.

Two total nits:
a. Comma before "which", please.
b. The "for example" needs some rewording to make it work:
NEW
   For example, if an EST csrattrs request is followed by a
   simpleenroll request, both can use the same authenticated
   DTLS connection.
END

-- Section 5.1 --

   EST-coaps is targeted for low-resource networks with small packets.
   Two types of installations are possible (1) rigid ones where the
   address and the supported functions of the EST server(s) are known,
   and (2) flexible one where the EST server and it supported functions
   need to be discovered.

This needs a colon (:) after "possible", a comma after "rigid ones", "a" before
"flexible one", another comma after "flexible one", and make it "its supported".

-- Section 5.5 --

   Similarly, 2.04

   is used in successfull response to EST-coaps POST requests (/sen,
   /sren, /skg, /skc).

There's odd spacing here; please fix it.  And "successful" is misspelled.

-- Section 5.7 --

   If the server is very slow (i.e., minutes) in providing the response
   (i.e., when a manual intervention is needed),

I think you mean "e.g." for both of those, evidence for my general aversion to
using Latin abbreviations that many people don't fully understand.  It also
feels odd to have the two examples separated in this way.  I suggest this:

NEW
   If the server is very slow in providing the response (for example,
   manual intervention is required and it could take minutes  for it
   to respond),
END

   it SHOULD respond with
   an ACK containing response code 5.03 (Service unavailable) and a Max-
   Age Option to indicate the time the client SHOULD wait to request the
   content later.

Perhaps, "to indicate the time the client SHOULD wait before sending another
request to obtain the content." ?

   After a delay of Max-Age, the client SHOULD resend
   the identical CSR to the server.  As long as the server responds with
   response code 5.03 (Service Unavailable) with a Max-Age Option, the
   client SHOULD keep resending the enrollment request until the server
   responds with the certificate or the client abandons the request for
   other reasons.

That last sentence reads very strangely to me.  It SHOULD keep resending the
request until it decides to stop?  What does that actually mean?

Maybe what you're really trying to say is something like this?:

NEW
   As long as the server continues responding with
   response code 5.03 (Service Unavailable) with a Max-Age Option, the
   client will continue to delay for Max-Age and then resend the
   enrollment request until the server responds with the certificate or
   the client abandons the request for policy or other reasons.
END

-- Section 5.8 --

   In scenarios where it is desirable that the server generates the
   private key, server-side key generation is available.

This seems like a content-free sentence.  Maybe this?:

NEW
   Private keys can be generated on the server.  Scenarios where
   that makes sense include those where it is considered more
   secure...
END

   Of course, that does not eliminate the
   need for proper random numbers in various protocols like (D)TLS
   (Section 10.1).

May I suggest this?:

NEW
   As always, it is necessary to use proper random numbers in
   various protocols such as (D)TLS (Section 10.1).
END

   server or proxy to generate the private key and the certificate which
   are transferred back to the client

Needs a comma before "which".

   or the asymmetric keypair establishment method is out of scope of the
   specification.

"of this specification".

   [I-D.ietf-core-multipart-ct] containing a CBOR array with four items

   (Section 5.3)

   .  The two representations

More odd spacing.

   Dependent on the request, the
   private key can be in unprotected PKCS#8 [RFC5958] format

"Depending upon the request"

   In
   the case where the asymmetric encryption key is suitable for
   transport key operations the generated private key is encrypted with
   a symmetric key which is encrypted by the client-defined (in the CSR)
   asymmetric public key and is carried in an encryptedKey attribute in
   a KeyTransRecipientInfo structure.

Long sentence that needs punctuation: comma after "operations", comma before
"which", comma before "and".  Also, I would move "(in the CSR)" a few words
later, after "public key".

-- Section 7 --

   It is recommended, based on experiments,

   to follow the default CoAP configuration parameters ([RFC7252]).

Odd spacing, again.  But "it is recommended to follow" is also odd English.  I
suggest making this active, rather than passive, thus:

NEW
   Implementations should follow the default CoAP configuration
   parameters ([RFC7252]).
END

I don't think the "based on experiments" bit adds anything, but if you want to
keep it you can prepend "Experiments have shown that" to my suggestion.

-- Section 9.1 --
Don't you want to remove the "TBD" on "TBD287" here?  Wasn't the "TBD" just a
flag to remind people that it hadn't been formally allocated yet?

— Section 10.1 —

   It is important to note that sources contributing to the randomness
   pool used to generate random numbers on laptops or desktop PCs are
   not available on many constrained devices, such as mouse movement,
   timing of keystrokes, or air turbulence on the movement of hard drive
   heads, as pointed out in [PsQs].

The sentence order is wrong here.  For example, mouse movement is not a
constrained device.  The correct order is more like this:

NEW
   It is important to note that, as pointed out in [PsQs], sources
   contributing to the randomness pool used to generate random
   numbers on laptops or desktop PCs, such as mouse movement,
   timing of keystrokes, or air turbulence on the movement of hard
   drive heads, are not available on many constrained devices.
END